Irregular inflammation is a major component of a wide range of human diseases. People suffering from degenerative disorders often exhibit excess levels of pro-inflammatory regulators in their blood. One type of such pro-inflammatory regulators are cytokines including IL-1α, β, IL-2, IL-3, IL-6, IL-7, IL-9, IL-12, IL-17, IL-18, IL-23, TNF-α, LT, LIF, Oncostatin, and IFNc1α, β, γ.
A non-limiting list of common medical problems that are directly caused by inflammatory cytokines include: arthritis where inflammatory cytokines can lead to lesions in the synovial membrane and destruction of joint cartilage and bone; kidney failure where inflammatory cytokines restrict circulation and damage nephrons; lupus where inflammatory cytokines exacerbate immune complex deposition and damage; asthma where inflammatory cytokines close the airway; psoriasis where inflammatory cytokines induce dermatitis; pancreatitis where inflammatory cytokines induce pancreatic cell injury; allergy where inflammatory cytokines induce vasopermeability and congestion; fibrosis where inflammatory cytokines attack traumatized tissue; surgical complications where inflammatory cytokines prevent healing; anemia where inflammatory cytokines attack erythropoietin production; and fibromyalgia where inflammatory cytokines are elevated in fibromyalgia patients.
Other diseases associated with chronic inflammation include cancer; heart attack where chronic inflammation contributes to coronary atherosclerosis; Alzheimer's disease where chronic inflammation destroys brain cells; congestive heart failure where chronic inflammation causes heart muscle wasting; stroke where chronic inflammation promotes thrombo-embolic events; and aortic valve stenosis where chronic inflammation damages heart valves. Arteriosclerosis, osteoporosis, Parkinson's disease, infection, inflammatory bowel disease including Crohn's disease and ulcerative colitis as well as multiple sclerosis (a typical autoimmune inflammatory-related disease) are also related to inflammation (Bebo, B. F., Jr., J Neurosci Res, 45: 340-348, (1996); Mennicken, F., Trends Pharmacol Sci, 20: 73-78, (1999); Watanabe, T, Int J Cardiol, 66 Suppl 1: S45-53; discussion S55, (1998); Sullivan, G. W., J Leukoc Biol, 67: 591-602, (2000); Franceschi, C., Ann N Y Acad Sci, 908: 244-254, (2000); Rogers, J, Ann N Y Acad Sci, 924: 132-135, (2000); Li, Y. J., Hum Mol Genet, 12: 3259-3267, (2003); Maccarrone, M., Curr Drug Targets Inflamm Allergy, 1: 53-63, (2002); Lindsberg, P. J., Stroke, 34: 2518-2532, (2003); DeGraba, T. J., Adv Neurol, 92: 29-42, (2003); Ito, H., Curr Drug Targets Inflamm Allergy, 2: 125-130, (2003); von der Thusen, J. H., Pharmacol Rev, 55: 133-166, (2003); Schmidt, M. I., Clin Chem Lab Med, 41: 1120-1130, (2003); Virdis, A., Curr Opin Nephrol Hypertens, 12: 181-187, (2003); Tracy, R. P., Int J Clin Pract, Suppl 10-17, (2003); Haugeberg, G., Curr Opin Rheumatol, 15: 469-475, (2003); Tanaka, Y., J Bone Miner Metab, 21: 61-66, (2003); Williams, J. D., Clin Exp Dermatol, 27: 585-590, (2002)). Some diseases in advanced stages can be life threatening. Several methodologies are available for the treatment of such inflammatory diseases; the results, however, are generally unsatisfactory as evidenced by a lack of efficacy and drug related side effects associated therewith.
Inflammatory Bowel Disease
Inflammatory bowel disease (IBD) comprises Crohn's disease (CD) and ulcerative colitis (UC), both of which are idiopathic chronic diseases occurring with an increasing frequency in many parts of the world. In the United States, more than 600,000 are affected every year. IBD can involve either small bowel, large bowel, or both. CD can involve any part of the gastrointestinal tract, but most frequently involves the distal small bowel and colon. It either spares the rectum, or causes inflammation or infection with drainage around the rectum. UC usually causes ulcers in the lower part of the large intestine, often starting at the rectum. Patients with IBD have defective intestinal epithelial barrier function, which allows bacterial colonization of the epithelia. As a result, bacterial products and pro-inflammatory cytokines (TNF-α, IL-1 and IL-6) cause persistent inflammatory stimulation. Bacterial antigens are introduced into the immune system by mucosal dendritic cells and macrophases. In response, intestinal phagocytes (mainly monocytes and neutrophils) proliferate and increase expression and secretion of pro-inflammatory cytokines. Symptoms vary but may include diarrhea, fever, and pain. Patients with prolonged UC are at an increased risk of developing colon cancer. There is currently no satisfactory treatment, as the cause for IBD remains unclear although infectious and immunologic mechanisms have been proposed. IBD treatments aim at controlling inflammatory symptoms, conventionally using corticosteroids, aminosalicylates and standard immunosuppressive agents such as azathioprine (6-mercaptopurine), methotrexate and ciclosporine. Of these, the only disease-modifying therapies are the immunosuppressive agents azathioprine and methotrexate, both of which have a slow onset of action and only a moderate efficacy. Long-term therapy may cause liver damage (fibrosis or cirrhosis) and bone marrow suppression. Also patients often become refractory to such treatment. Other therapeutic regimes merely address symptoms (Rutgeerts, P. A, J Gastroenterol Hepatol, 17 Suppl: S176-185 (2002); Rutgeerts, P., Aliment Pharmacol Ther, 17: 185-192 (2003)).
Psoriasis
Psoriasis is one of the most common immune-mediated chronic skin diseases that comes in different forms and varied levels of severity, affecting approximately 2% of the population or more than 4.5 million people in the United States of which 1.5 million are considered to have a moderate to severe form of the disease. Ten to thirty percent of patients with psoriasis also develop a form of arthritis—psoriatic arthritis, which damages the bone and connective tissue around the joints. Psoriasis appears as patches of raised red skin covered by a flaky white buildup. It may also have a pimple-ish (pustular psoriasis) or burned (erythrodermic) appearance. Psoriasis may also cause intense itching and burning. Patients suffer psychologically as well as physically. Several modalities are currently available for treatment of psoriasis, including topical treatment, phototherapy, and systemic applications. However, they are generally considered to be only disease suppressive and disease modifying; none of them are curative. Moreover, many treatments are either cosmetically undesirable, inconvenient for long-term use, or associated with significant toxicity.
There are several types of psoriasis. Plaque psoriasis (psoriasis vulgaris) is the most common form of psoriasis. It affects 80 to 90% of people with psoriasis. Plaque psoriasis typically appears as raised areas of inflamed skin covered with silvery white scaly skin. These areas are called plaques. Flexural psoriasis (inverse psoriasis) appears as smooth inflamed patches of skin. It occurs in skin folds, particularly around the genitals (between the thigh and groin), the armpits, under an overweight stomach (pannus), and under the breasts (inframammary fold). It is aggravated by friction and sweat, and is vulnerable to fungal infections. Guttate psoriasis is characterized by numerous small oval (teardrop-shaped) spots. These numerous spots of psoriasis appear over large areas of the body, such as the trunk, limbs, and scalp. Guttate psoriasis is associated with streptococcal throat infection. Pustular psoriasis appears as raised bumps that are filled with non-infectious pus (pustules). The skin under and surrounding pustules is red and tender. Pustular psoriasis can be localised, commonly to the hands and feet (palmoplantar pustulosis), or generalised with widespread patches occurring randomly on any part of the body. Nail psoriasis produces a variety of changes in the appearance of finger and toe nails. These changes include discolouring under the nail plate, pitting of the nails, lines going across the nails, thickening of the skin under the nail, and the loosening (onycholysis) and crumbling of the nail. Psoriatic arthritis involves joint and connective tissue inflammation. Psoriatic arthritis can affect any joint but is most common in the joints of the fingers and toes. This can result in a sausage-shaped swelling of the fingers and toes known as dactylitis. Psoriatic arthritis can also affect the hips, knees and spine (spondylitis). About 10-15% of people who have psoriasis also have psoriatic arthritis. Erythrodermic psoriasis involves the widespread inflammation and exfoliation of the skin over most of the body surface. It may be accompanied by severe itching, swelling and pain. It is often the result of an exacerbation of unstable plaque psoriasis, particularly following the abrupt withdrawal of systemic treatment. This form of psoriasis can be fatal, as the extreme inflammation and exfoliation disrupt the body's ability to regulate temperature and for the skin to perform barrier functions.
With increased understanding of the biological properties of psoriasis over the past two decades, biologic therapies targeting the activity of T lymphocytes and cytokines responsible for the inflammatory nature of this disease have become available. Currently, drugs prescribed for psoriasis include TNF-α inhibitors initially used for rheumatoid arthritis (RA) treatment, ENBREL® (etanercept), REMICADE® (infliximab) and HUMIRA® (adalimumab), and T-cell inhibitor AMEVIVE® (alefacept) from Biogen approved in 2002 and RAPTIVA® (efalizumab) from Genentech/Xoma approved in 2003 (Weinberg, J. M., J Drugs Dermatol, 1: 303-310, (2002)). AMEVIVE® (alefacept) is an immunoglobulin fusion protein composed of the first extracellular domain of human LFA-3 fused to the hinge, C(H)2 and C(H)3 domains of human IgG(1). It inhibits T cell proliferation through NK cells (Cooper, J. C., Eur J Immunol, 33: 666-675, (2003)). RAPTIVA® is also known as anti-CD11a, a humanized monoclonal antibody which targets the T cell adhesion molecule, leukocyte function-associated antigen-1 (LFA-1). Prevention of LFA-1 binding to its ligand (ICAM-1, intercellular adhesion molecule-1) inhibits lymphocyte activation and migration, resulting in a decreased lymphocyte infiltration, thereby limiting the cascade of events eventually leading to the signs and symptoms of psoriasis (Cather, J. C., Expert Opin Biol Ther, 3: 361-370, (2003)). Potential side effects for current TNF-α inhibitors of the prior art, however, are severe, including development of lymphoma (Brown, S. L., Arthritis Rheum, 46: 3151-3158, (2002)), worsening congestive heart failure, resulting in a serious infection and sepsis, and exacerbations of multiple sclerosis and central nervous system problems (Weisman, M. H., J Rheumatol Suppl, 65: 33-38, (2002); Antoni, C., Clin Exp Rheumatol, 20: S152-157, (2002)). While side effects of the T-cell inhibitor of AMEVIVE®/RAPTIVA® may be more tolerable in psoriasis treatment, RAPTIVA® is an immunosuppressive agent. Immunosuppressive agents have the potential to increase the risk of infection, reactivate latent, chronic infections or increase the risk of cancer development.
Although many advances have been made in the understanding of the biological properties of psoriasis over the past two decades and an unconventional treatment for psoriasis has become available as described above, much of the suffering it produces is still not adequately addressed. A survey of over 40,000 American patients with psoriasis performed by the National Psoriasis Foundation in 1998 showed 79% of the younger patients felt frustrated by the ineffectiveness of their treatment. Of those with severe disease, 32% felt their treatment was not aggressive enough (Mendonca, C. O., Pharmacol Ther, 99: 133-147, (2003); Schon, M. P., J Invest Dermatol, 112: 405-410, (1999)).
Rheumatoid Arthritis
Rheumatoid arthritis (RA) represents another example of troublesome inflammatory disorders. It is a common chronic inflammatory-related disease characterized by chronic inflammation in the membrane lining (the synovium) of the joints and/or other internal organs. The inflammatory cells can also invade and damage bone and cartilage. The joint involved can lose its shape and alignment, resulting in loss of movement. Patients with RA have pain, stiffness, warmth, redness and swelling in the joint, and other systemic symptoms like fever, fatigue, and anemia. Approximately 1% of the population or 2.1 million in the U.S. are currently affected, of which more are women (1.5 million) than men (0.6 million). The pathology of RA is not fully understood although the cascade of improper immunological reactions has been postulated as a mechanism. Conventional treatment is unfortunately inefficient in RA (Bessis, N., J Gene Med, 4: 581-591, (2002)) (29). The disease does not respond completely to symptomatic medications including corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs) used since the 1950s. Also, these medications carry a risk of serious adverse effects. The therapeutic effects of the disease-modifying antirheumatic drugs (DMARDs) such as Methotrexate (MTX) are often inconsistent and short-lived.
The role of the cytokine network in mediating inflammation and joint destruction in RA has been extensively investigated in recent years. In addition to TNF-α, IL-1 plays a pivotal role in the pathogenesis and the clinical manifestations of RA (54). The ability of IL-1 to drive inflammation and joint erosion and to inhibit tissue repair processes has been clearly established in in vitro systems and in animal models, and alleviation of inflammatory symptoms in RA patients has been achieved by blockage of IL-1 (Bresnihan, B., Arthritis Rheum, 41: 2196-2204, (1998)). IL-6 is a multifunctional cytokine that regulates the immune response, hematopoiesis, the acute phase response, and inflammation. Deregulation of IL-6 production is implicated in the pathology of several diseases including RA. A therapeutic approach to block the IL-6 signal has been carried out by using humanized anti-IL-6R antibody for RA among other diseases (Ito, H., Curr Drug Targets Inflamm Allergy, 2: 125-130, (2003); Ishihara, K Cytokine Growth Factor Rev, 13: 357-368, (2002)). IL-10 is an anti-inflammatory cytokine. Expressing IL-10 has been shown to prevent arthritis or ameliorate the disease in animal models (57, 58). While it is obvious that cytokines such as TNF-α, IL-1, IL-6 and IL-10 have independent roles, they act in concert in mediating certain pathophysiological processes in RA. The finding of a class of molecules described in this invention, which are able to modulate these different cytokines, will result in dramatic therapeutic progress in the treatment of RA.
A new class of biologic DMARDs (disease-modifying antirheumatic drugs) for the treatment of RA has recently been developed based on an understanding of the role of cytokines, TNF-α and IL-1, in the inflammatory process. The FDA has approved several such DMARDs including ENBREL® (etanercept) from Immunex/Amgen Inc. in 1998, REMICADE® (infliximab) from Centocor/Johnson & Johnson, HUMIRA® (adalimumab) from Abbott Laboratories Inc. in 2002, and KINERET® (anakinra) from Amgen in 2001. ENBREL® is a soluble TNF receptor (TNFR) recombinant protein. REMICADE® is a humanized mouse (chimeric) anti-TNF-α monoclonal antibody. HUMIRA® is a fully human anti-TNF monoclonal antibody created using phage display technology resulting in an antibody with human-derived heavy and light chain variable regions and human IgG1:k constant regions. All these 3 protein-based drugs target and bind to TNF-α to block the effects of TNF-α. KINERET® is a recombinant IL-1 receptor antagonist, which is similar to native human IL-1Ra, except for the addition of a single methionine residue at its amino terminus. KINERET® blocks the biologic activity of IL-1 by competitively inhibiting IL-1 binding to the IL-1 type I receptor (IL-1RI) and consequently reducing the pro-inflammatory effects of IL-1.
Multiple Sclerosis
Multiple Sclerosis (MS) is an autoimmune disease diagnosed in 350,000 to 500,000 people in the United States. Multiple areas of inflammation and loss of myelin in the brain and spinal cord signify the disease. Patients with MS exhibit varied degrees of neurological impairment depending on the location and extent of the loss of the myelin. There is evidence that the expression of chemokines (IL-8 family members) during CNS autoimmune inflammation is regulated by some pro-inflammatory cytokines, such as TNF (Glabinski, A. R., Scand J Immunol, 58: 81-88, (2003)). The roles of other pro-/anti-inflammatory cytokines such as IL-1.beta., IL-6 and IL-10 were also confirmed in EAE animal models (Diab, A., J Neuropathol Exp Neurol, 56: 641-650, (1997); Samoilova, E. B., J Immunol, 161: 6480-6486, (1998); Robertson, J., J Cell Biol, 155: 217-226, (2001)) as well as in humans (de Jong, B. A., J Neuroimmunol, 126: 172-179, (2002)). IL-1β is present in MS lesions. IL-1 receptor antagonist (IL-1Ra) moderates the induction of experimental autoimmune encephalomyelitis (EAE). Increased risk of MS has been seen in individuals with High IL-1 (3 over IL-1Ra production ratio and high TNF over IL-10 production ratio (de Jong, B. A., J Neuroimmunol, 126: 172-179, (2002)). Common symptoms of MS include fatigue, weakness, spasticity, balance problems, bladder and bowel problems, numbness, vision loss, tremors and depression. Current treatment of MS only alleviates symptoms or delays the progression of disability, and several new treatments for MS including stem cell transplantation and gene therapy are conservatory (Fassas, A., Blood Rev, 17: 233-240, (2003); Furlan, R., Curr Pharm Des, 9: 2002-2008, (2003)). While anti-TNF antibodies have shown protective effects in experimental autoimmune encephalomyelitis (EAE), they aggravate the disease in MS patients, suggesting that inhibition of TNF-α alone is not sufficient (Ghezzi, P., Neuroimmunomodulation, 9: 178-182, (2001)).
Neurodegenerative Disorders
Alzheimer's disease (AD) and Parkinson's disease (PK) are the two most common neurodegenerative disorders. AD seriously affects a person's ability to carry out daily activities. It involves the parts of the brain that control thought, memory, and language. About 4 million Americans, usually after age 60, are estimated to suffer from AD.
PK is a progressive disorder of the central nervous system affecting over 1.5 million people in the United States. Clinically, the disease is characterized by a decrease in spontaneous movements, gait difficulty, postural instability, rigidity and tremor. PK is caused by the degeneration of the pigmented neurons in the substantia nigra of the brain, resulting in decreased dopamine availability. The causes of these neurodegenerative disorders are unknown and there is currently no cure for the disease.
Thus, novel approaches for the treatment of the above and other inflammatory-related diseases are needed. Although inflammatory-related disease mechanisms remain unclear and often vary from each other, dysfunction of the immune system caused by deregulation of cytokines has been demonstrated to play an important role in the initiation and progression of inflammation (Schon, M. P., J Invest Dermatol, 112: 405-410, (1999); Andreakos, E. T., Cytokine Growth Factor Rev, 13: 299-313, (2002); Najarian, D. J., J Am Acad Dermatol, 48: 805-821, (2003)).
Post-Radiotherapy Related Inflammation:
Radiation damage related inflammatory diseases to the rectum and sigmoid colon are most common complications with radiation therapy for cancers in the pelvic region, which include cancers of the cervix, uterus, prostate, bladder, and testes. Radiation proctosigmoiditis is the most common clinically apparent form of colonic damage after pelvic irradiation with an incidence of 5% to 20%. Patients typically exhibit symptoms of tenesmus, bleeding, low-volume diarrhea, and rectal pain. Rarely, low-grade obstruction or fistulous tracts into adjacent organs may develop.
Cytokines can be generally classified into 3 types: pro-inflammatory (IL-1α, β, IL-2, IL-3, IL-6, IL-7, IL-9, IL-12, IL-17, IL-18, IL-23, TNF-α, LT, LIF, Oncostatin, and IFNc1α, β, γ); anti-inflammatory (IL-4, IL-10, IL-11, W-13 and TGF-β); and chemokines (IL-8, Gro-α, MIP-1, MCP-1, ENA-78, and RANTES).
Tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) are proinflammatory cytokines that mediate inflammatory responses associated with infectious agents and other cellular stresses. Overproduction of cytokines such as IL-1 and TNF-α is believed to underlie the progression of many inflammatory diseases including rheumatoid arthritis (RA), Crohn's disease, inflammatory bowel disease, multiple sclerosis, endotoxin shock, osteoporosis, Alzheimer's disease, congestive heart failure, and psoriasis among others (Dinarello, C. A. et al., Rev. Infect. Diseases 1984, 6:51; Salituro et al., Curr. Med. Chem. 1999, 6:807-823; Henry et al., Drugs Fut. 1999, 24:1345-1354). An accepted therapeutic approach for potential drug intervention in these conditions is the reduction of proinflammatory cytokines such as TNF-α (also referred to as TNFa) and interleukin-1β (IL-1b).
Phosphodiesterase4
The cyclic nucleotide specific phosphodiesterases (PDEs) represent a family of enzymes that catalyze the hydrolysis of various cyclic nucleoside monophosphates (including cAMP and cGMP). These cyclic nucleotides act as second messengers within cells, and as messengers, carry impulses from cell surface receptors having bound various hormones and neurotransmitters. PDEs act to regulate the level of cyclic nucleotides within cells and maintain cyclic nucleotide homeostasis by degrading such cyclic mononucleotides resulting in termination of their messenger role.
PDE enzymes can be grouped into eleven families according to their specificity toward hydrolysis of cAMP or cGMP, their sensitivity to regulation by calcium, calmodulin or cGMP, and their selective inhibition by various compounds. For example, PDE 1 is stimulated by Ca2+/calmodulin. PDE 2 is cGMP-dependent, and is found in the heart and adrenals. PDE 3 is cGMP-dependent, and inhibition of this enzyme creates positive inotropic activity. PDE 4 is cAMP specific, and its inhibition causes airway relaxation, antiinflammatory and antidepressant activity. PDE 5 appears to be important in regulating cGMP content in vascular smooth muscle, and therefore PDE 5 inhibitors may have cardiovascular activity. Since the PDEs possess distinct biochemical properties, it is likely that they are subject to a variety of different forms of regulation.
PDE4 is distinguished by various kinetic properties including low Michaelis constant for cAMP and sensitivity to certain drugs. The PDE4 enzyme family consists of four genes, which produce 4 isoforms of the PDE4 enzyme designated PDE4A, PDE4B, PDE4C, and PDE4D [See: Wang et al., Expression, Purification, and Characterization of human cAMP-Specific Phosphodiesterase (PDE4) Subtypes A, B, C, and D, Biochem. Biophys. Res. Comm., 234, 320 324 (1997)] In addition, various splice variants of each PDE4 isoform have been identified.
PDE4 isoenzymes are localized in the cytosol of cells and are unassociated with any known membranous structures. PDE4 isoenzymes specifically inactivate cAMP by catalyzing its hydrolysis to adenosine 5′-monophosphate (AMP). Regulation of cAMP activity is important in many biological processes, including inflammation and memory. Inhibitors of PDE4 isoenzymes such as rolipram, piclamilast, CDP-840 and ariflo are powerful antiinflammatory agents and therefore may be useful in treating diseases where inflammation is problematic such as asthma or arthritis. Further, rolipram improves the cognitive performance of rats and mice in learning paradigms.
Compounds which can inhibit the biological moieties described above, or treat diseases involving those biological moieties, would be a significant advance in the art.